Month: January 2019

Together with URE and AMSAT-EA, I have presented a proposal for the upcoming IARU R1 Vienna interim meeting 2019 addressing the problems derived from the use of Amateur satellite spectrum by universties, research institutions and private companies. The title of the proposal is “Satellites transmitting on Amateur bands with undocummented protocols or without permission”, and the text of the proposal can be found here.

This proposal addresses the problems caused both by satellites that are using undocummented protocols for their telemetry, so Amateurs are unable to decode their signals, and satellites that are transmitting without having obtained the appropriate IARU frequency coordination.

The number of small satellites that are launched each year seems to be growing steadily, and many satellite developers are resorting to the Amateur satellite service as a way to obtain free spectrum access, regardless of whether their mission fits the requirements for an Amateur satellite. I think that we must try to defend our Amateur bands and ensure that proper use is made of them. Hopefully this proposal is a first step in making people aware of the problem and trying to find solutions.

If you’ve been following my posts about Es’hail 2, you’ll know that shortly after launch Es’hail 2 was stationed in a test slot at 24ºE. It remained in this slot until December 29, when it started to move to its operational slot at 26ºE. As of January 2, Es’hail is now stationed at 26ºE (25.8ºE, according to the TLEs).

The new GEO orbit at 26ºE is much more perfect than the orbit it had at 24ºE. This is to be expected for an operational orbit. Since December 30, I’ve been recording Doppler data of the satellite moving to its operational slot, and I have found some interesting effects of orbital dynamics in the data. This post is an account of these.

Recently, the STRF satellite tracking toolkit for radio observations by Cees Bassa has been gaining some popularity. This toolkit allows one to process RF recordings to extract frequency measurements and perform TLE matching and optimization via Doppler curves. Unfortunately, there is not a lot of documentation for this toolkit. There are some people that want to use STRF but don’t have a clear idea of where to start.

While I have tested very briefly STRF in the past, I had never used it for doing any serious task, so I’m also a newcomer. I have decided to test this tool and learn to use it properly, writing some sort of walk-through as I learn the main functionality. Perhaps this crash course will be useful to other people that want to get started with STRF.

As I have said, I’m no expert on STRF, so there might be some mistakes or omissions in this tutorial that hopefully the experts of STRF will point out. The crash course is organized as a series of exercises that explain basic concepts and the workflow of the tools. The exercises revolve around an IQ recording that I made of the QB50 release from ISS in May 2017. That recording is interesting because it is a wide band recording of the full 70cm Amateur satellite band on an ISS pass on May 29. During a few days before this, a large number of small satellites had been released from the ISS. Therefore, this recording is representative of the TLE lottery situation that occurs after large launches, where the different satellites haven’t drifted much yet and one is trying to match each satellite to a TLE.

The IQ recording can be downloaded here (16GB). I suggest that you download it and follow the exercises on your machine. After you finish all the exercises, you can invent your own. Certainly, there is a lot that can be tried with that recording.

A number of supporting files are created during the exercises. For reference, I have created a gist with these files.